Color diffusion transfer film unit containing a temporary barrier for developer restrainers

ABSTRACT

FILM UNITS INCLUDING A NEGATIVE COMPONENT CONTAINING AT LEAST ONE LIGHT-SENSITIVER SILVER HALIDE LAYER AND ASSOCIATED DYE IMAGE-PROVIDING MATERIAL AND A POSITIVE COMPONENT CONTAINING AT LEAST A DYEABLE STRATUM, THE POSITIVE COMPONENT FURTHER INCLUDING A DEVELOPMENT RESTRAINER DISPOSED IN THE DYEABLE STRATUM AND/OR IN AN ASSOCIATED LAYER, PARTICULARLY SUCH FILM UNITS ADAPTED FOR FORMING COLOR TRANSFER IMAGES VIEWABLE WITHOUT SEPARATION, WHEREIN A LAYER IS DISPOSED BETWEEN THE DEVLOPMENT RESTRAINER AND THE NEGATIVE COMPONENT, WHICH LAYER IS SO CONSTITUTED AS TO PREVENT SUBSTANTIAL MIGRATION OF THE DEVELOPMENT RESTRAINER TO THE NEGATIVE COMPONET DURING THE SHELF   LIFE OF THE FILM BUT WHICH WILL PERMIT SUCH MIGRATION UPON APPLICATION OF AN AQUEOUS ALKALINE FLUID.

Dec. 19, 1972 COLOR DIFFUSIO R BA E Filed April 28 1971 L. H. AROND A ER FILM UNIT CON R R DEVELOPER REST NING A TEMPERARY NERS 2 Sheets-Sheet l SUPPORT CYAN DYE DEVELOPER LAYER REDSENS|TIVE SILVER HALIDE EMULSION LAYER /-INTER LAYER /-MAGENTA DYE DEVELOPER LAYER GREEN-SENSITIVE SILVER HALIDE EMULSION LAYER INTERLAYER YELLOW DYE DEVELOPER LAYER BLUE-SE m SILVER HALIDE I EMULsIQ LA E I AUXILLARY LAYER PTEMPQRARY BARRIER I |MAsEREcE|v|Ne LAYER SPACER LAYER /-NEUTRALIZING LAYER /SU PPORT FIG. I

NVEN TOR. LE R H. AROND EM and m a/rwl ATTORNEYS Dec. 19, 19/2 L. H. AROND 3,706,557

COLOR DIFFUSION TRANSFER FILM UNIT CONTAINING A TEMPERARY BARRIER FOR DEVELOPER RESTRAINERS Filed April 28, L971 2 Sheets-Sheet 2 SUPPORT |3-\ l cYAw DYE DEvELDPER LAYER PRED- SENSITIVE SILVER HALIDE |4- EMULSION LAYER |5 \Q/INTERLAYER \L \fMAGENTA DYE DEVELOPER LAYER |7- ,GREENSENSlTlVE SILVER HALIDE EMULSION LAYER |srlNTERLAYER 2 i9" W/YELLOW DYE DEVELOPER LAYER 2O\// BLUE-SENSITIVE SILVER HALIDE EMU LSION LAYER 24* SPACER LAYER -AUXILLARY LAYER lMAGE-REcElvlNG LAYER TEMPORARY BARRIER "NEUTRALIZING LAYER /-SUPPORT INVENTOR. LESTER H. AROND BY fivzaw rz and 772% and ATTORNEYS United States Patent us. or. 96-29 D 39 Claims ABSTRACT OF THE DISCLOSURE Film units including a negative component containing at least one light-sensitive silver halide layer and associated dye image-providing material and a positive component containing at least a dyeable stratum, the positive component further including a development restrainer disposed in the dyeable stratum and/or in an associated layer, particularly such film units adapted for forming color transfer images viewable without separation, wherein a layer is disposed between the development restrainer and the negative component, which layer is so constituted as to prevent substantial migration of the development restrainer to the negative component during the shelf life of the film but which will permit such migration upon application of an aqueous alkaline fluid.

This application is a continuation-in-part of application Ser. No. 99,544 filed Dec. 18, 1970 and now abandoned.

BACKGROUND OF THE INVENTION Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more dilfusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.

The dye image-providing materials which may be employed in such processes generally may be characterized as either (I) initially soluble or difi'usible in the processing composition but are selectively rendered non-diifusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-ditfusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

As examples of initially soluble or diffusible materials and their application in color dilfusion transfer, mention may be made of those disclosed, for example, in US. Patents Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-difiusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Patents Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.

In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the socalled tripack structures employing a blue-, a greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.

A particularly useful system for forming color images by diffusion transfer is that described in US. Patent No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye imageproviding materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated, therewith (in the same or in an adjacent layer) is developed by applying an aqueous alkaline processing composition. Exposed and developable silver halide is developed by the dye developer which in turn becomes oxidized to provide an oxidation product which is appreciably less ditfusible than the unreacted dye developer, thereby providing an imagewise distribution of dilfusible dye developer in terms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, by dilfusion, to a dyeable stratum to impart thereto a positive dye transfer image. Multicolor images may be obtained with a photosensitive element having two or more selectively sensitized silver halide layers and associated dye developers, a tripack structure of the type described above and in various patents including the aforementioned US. Patent No. 2,983,606 being especially suitable for accurate color recordation of the original subject matter.

In diffusion transfer processes of this type employing an integral multilayer negative processed with a common processing composition, the dye image-providing material diffusing from an underlying photosensitive layer must necessarily pass through at least one other overlying photosensitive layer. Thus, for example, in systems employing dye developers, if the unoxidized dye developer dilfusing from an underlying layer enters an overlying silver halide, there is as much likelihood that this diffusing dye developer from the underlying layer will react (develop the silver halide layer to which it has dilfused) as there is that the dye developer initially associated with this layer will react.

To illustrate this problem, reference may be made to the aforementioned tripack multilayer element comprising a red-, a greenand a blue-sensitive silver halide layer having associated therewith, respectively, a cyan, a magenta and a yellow dye developer. Assuming that, in a given area of the element, exposure is elfected only of the green-sensitive silver halide layer, theoretically, and ideally, this exposed area should be developed by the associated magenta dye developer which is in turn oxidized, so that only cyan and blue dye developer should be transferred by diffusion to the dyeable stratum. If the magenta dye developer has substantially completed this development of the ldevelopable green-sensitive silver halide prior to arrival of the unoxidized diifusing cyan dye developer, no harm will be done. On the other hand, if the diffusing unoxidized cyan dye developer diffuses into the green-sensitive layer while appreciable undeveloped but developable green-sensitive silver halide is still present, this cyan dye developer will react (develop), since it will not distinguish between developable silver halides of different color sensitivity. This reaction with the wrong silver halide gives rise to the phenomenon referred to as cross-talk which is evidenced by producing multicolor transfer images having reduced color separation. In the instance given, this is manifested by less cyan density caused by unwanted immobilization of diflusing cyan dye developer by reaction with the redsensitive silver halide layer and probably increased magenta density due to the inopportunity for the magenta dye developer to react as intended and hence be immobilized. The same phenomenon is noted with cyan and/or magenta dye developer diffusing through the blue-sensitive layer en route to the dyeable stratum. The total result of this cross-talk is the production of a color print having something less than optimum faithful or accurate color rendition of the subiect matter to be reproduced.

As is described and claimed in US. Pat. No. 3,265,498, this problem may be obviated by employing a development restrainer to cause the developable silver halide emaining after a predetermined time following application of the processing composition to be rendered undevelopable, so that unoxidized dye developer diifusing through an overlying silver halide layer other than the one to which it was initially associated in the film unit will not be immobilized by development of developable silver halide contained therein. Since this reagent effectively re'strains or arrests further development of developable silver halide after this predetermined period, which may, for example, be somewhere on the order of five to twenty seconds, such reagents employed for this purpose may be referred to as development restrainers and are so designated in the present application. While such reagents frequently will have characteristics similar to reagents commonly referred to as antifoggants, they perform a function different from what is normally con templated as the function of an antifoggant, i.e., their function is not to reduce the fog density in unexposed areas, although under some circumstances they may also perform this function to a small degreel Reagents which are particularly suitable for use as development restrainers are those which will form prod ucts or complexes with undeveloped silver halide, whether exposed or unexposed, but at least with exposed silver halide, which products are substantially less developable by a silver halide developing agent, e.g., by the dye developer, and which are substantially insoluble, and hence essentially undevelopable, i.e., developable only with difiiculty. As examples of useful development restrainers, mention may be made of heterocyclic mercaptans such as mercaptotetrazoles and mercaptobenzothiazoles, e.g., 1 phenyl-S-mercaptotetrazole, Z-mercaptobenzothiazole, etc.

In order to obtain the desired predetermined period during which development is effected without interference from the development restrainer, this reagent should be employed in a chemical form or in a physical location such that its availability to the developable silver halide is limited or restricted, e.g., as a result of the distance through which it must diffuse to reach the developing silver halide, or as a consequence of a significantly lower diffusion rate than the developing agents. Where the development restrainer is at least initially substantially slower in diffusion than the developing agent, e.g., the dye developer, as for example, as a result of the inclusion of a relatively long chain alkyl group or other such substituent, the development restrainer may be positioned in a layer of the multilayer photosensitive element. However, the preferred development restrainers are characterized as being readily ditfusible in the processing composition, e.g., an aqueous alkaline solution, and hence must be located sufficiently remote physically so as not to interfere with the desired development. This is typically accomplished by incorporating the reagent in the imagereceiving element adapted for placement in superposition with the photosensitive element during development and the resulting color transfer image formation. It may be placed in the dyeable stratum itself, in an overlying layer or in an underlying layer.

The present invention is directed to film units for forming color images by diffusion transfer wherein the negative component including the silver halide layer or layers and associated color-providing material and the positive component including the dyeable stratum are maintained in superposition at least during storage and in particular to those film units containing a negative or photosensitive component and a positive or imagereceiving component in the same structure, as distinguished from those color diffusion transfer systems wherein the photosensitive and image-receiving elements are separate structures adapted to be brought in superposition at some time after photoexposu're, e.g., during processing. In: particular, it is directed to film units and system of this nature employing dye image-providing materials such as those mentioned above and disclosed in the aforementioned illustrative patents wherein it is desired to employ a relatively mobile development restrainer in a position remote from the photosensitive strata, e.g., in the dyeable stratum or an associated layer. Of particular interest are those integral or composite film units which are adapted for forming a color reflection print viewable without separation from the remainder of the film unit and which will be described in detail hereinafter. In general, such film units comprise two or more light-sensitive layers and associated dye image-providing material, e.g., the aforementioned tripack structure, a superposed dyeable stra tum and means for applying a reflecting layer between the photosensitive strata and the dyeable stratum so as to mask effectively the photosensitive strata and to pro vide a background for viewing the dye image formed on the overlying dyeable stratum, without separation, by reflected light.

With such film units, it is also desirable to employ a development restrainer in the dyeable stratum or in an associated layer, e.g., in a layer positioned on the side of the dyeable stratum opposed from the photosensitive strata. However, it has been found that attempts to provide a readily soluble and diifusible development restrainer in such a structure presents certain inherent problems not found when the restrainer is incorporated in an image-receiving element adapted to be maintained separate from the photosensitive element until placed in superposition for development and diffusion transfer image formation. Specifically, it has been found that where the development restrainer is incorporated in the positive structure in such unitary film units, a portion of this reagent tends to diffuse during the shelf life of the unit from the layer in which it was incorporated to one or more of the light-sensitive layers, thereby restraining the desired development of exposed and developable areas. In other words, this premature and unwanted diffusion places the reagent in contact with the photosensitive layer or layers prior to application of the processing composition rather than at the desired predetermined interval after development has been initiated, which in turn causes improper dye transfer and the resulting loss of quality in the transfer image. This problem may be referred to as contamination caused by unwanted diffusion of the reagent from the layer in which it was positioned at some time between preparation of the film unit and its use. It may also be characterized as being an instability of the film unit, specifically an instability of the layer containing the development restrainer.

It is this problem to which the present invention is directed.

SUMMARY OF THE INVENTION The objectives of this invention are accomplished by including in the film unit between the negative component containing the photosensitive stratum or strata and associated dye image-providing material and the layer in the positive component containing the development restrainer a layer which is substantially impervious to moisture and will not permit migration of the development restrainer, at least to any significant extent, thereby effectively inhibiting contamination caused by this migration during the shelf life of the film, but which will, upon application of an aqueous alkaline fluid, e.g., an aqueous alkaline processing composition, permit such migration at the desired time in the development process so as to permit the desired development restraining function. Where this layer is disposed between the dyeable stratum and the negative component, it is preferably so constituted so as not to affect adversely the transfer of dye image-providing material from the negative component to the dyeable stratum or the rate of such transfer.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is an enlarged, fragmentary, diagrammatic, sectional view of a film unit contemplated by this invention; and FIG. 2 is a similar view of another film unit of this invention.

DESCRIPTION OF PREFERRED EMBODIMENT In the preferred embodiment, the film unit is a so-called tripack employing dye developers as the dye image-providing materials, the development restrainer is disposed in the dyeable stratum and/or in a layer contiguous to the surface of the dyeable stratum opposed from the nega tive component. Where the development restrainer is disposed in a layer on the side of the dyeable stratum opposed from the negative component, the layer inhibiting premature migration of the development restrainer is preferably disposed in the film unit between the dyeable stratum and the layer containing the development restrainer.

As was mentioned previously, the invention relates to so-called integral negative-positive film units for use in preparing color transfer images and, more particularly, to the employment of development restrainers in such film units.

A primary object of this invention, therefore, is to provide novel film units of the foregoing description and systems employing them to produce color images.

Another object is to provide novel means for preventing premature migration of a development restrainer incorporated in the positive component of film units of the foregoing description.

Still another object is to provide novel integral negative-positive film units wherein the positive component contains a development restrainer and wherein a layer is disposed between the layer containing this development restrainer and the negative component so constituted as to inhibit premature migration of the development restrainer from the positive component to the negative component but not to interfere with desired migration of the development restrainer when wanted during the development process.

Yet another object is to provide novel film units adapted for preparing a color transfer image in a layer which is viewable, without separation, as a reflection print.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a further understanding of the nature and objects of this invention reference should be had to the following detailed description taken in conjunction with the accompanying drawing.

As was mentioned previously the present invention is primarily directed to integral negative-positive film units, e.g., photographic products wherein the negative component (light-sensitive layer or layers and any associated strata) and positive component (receiving layer and any associated strata) are contained together as a unitary structure so that two components are laminated or otherwise secured in physical juxtaposition as a single structure. Generally, such film units comprise a plurality of essential layers including at least one light-sensitive silver halide and associated dye image-providing material and a dyeable stratum. Film units intended to provide multicolor images comprise two or more selectively sensitized silver halide layers each having associated therewith an appropriate dye image-providing material exhibiting desired spectral absorption characteristics. As was heretofore mentioned the most commonly employed negative components for forming multicolor images are of the tripack structure containing a blue-, a greenand a red-sensitive silver halide layer having associated therewith in the same or in a contiguous layer a yellow, a magenta and a cyan dye image-providing material respectively. Interlayers or spacer layers may if desired be provided between the respective silver halide layers and associated dye image-providing materials.

As was heretofore mentioned the present invention is directed in particular to those integral negative-positive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component containing the dye transfer image need not be separated from the negative component for viewing purposes. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer between the dyeable stratum and the negative component in order to mask effectively the silver image or images formed as a function of development of the silver halide layer or layers and any remaining associated dye image-providing material and to provide a background for viewing the color image formed in the dyeable stratum, without separation, by reflected light. This reflecting layer may comprise a preformed layer of a reflecting agent included in the essential layers of the film unit or the reflecting agent may be provided after photoexposure, e.g., -by including the reflecting agent in the processing composition. These essential layers are preferably contained on a transparent dimensionally stable layer or support member positioned closest to the dyeable stratum so that the resulting transfer image is viewable through this transparent layer. Most preferably another dimensionally stable layer which may be transparent or opaque is positioned on the opposed surface of the essential layers so that the aforementioned essential layers are sandwiched or confined between a pair of dimensionally stable layers or support members, at least one of each is transparent to permit viewing therethrough of a color transfer image obtained as a function of development of the exposed 'film unit in accordance with the known color diffusion transfer system such as will be detailed hereinafter. -In a particularly preferred form such film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted upon application of pressure of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the negative component. It will be appreciated that the film unit may optionally contain other layers performing specific desired functions, e.g., spacer layers, pH-reducing layers, etc.

Opacifying means may be provided on either side of the negative component so that the film unit may be processed in the light to provide the desired color transfer image. In a particularly useful embodiment such opacifying means comprise an opaque dimensionally stable layer or support member positioned on the free or outer surface of the negative component, i.e., on the surface of the film unit opposed from the positive component containing the dyeable stratum to prevent photoexposure by actinic light incident thereon from this side of the film unit and an opacifying agent applied during development between the dyeable stratum and the negative component, e.g., by including the opacifying agent in a developing composition so applied, in order to prevent further exposure (fogging) by actinic light incident thereon from the other side of the film unit when the thus exposed film unit is developed in the light. The last-mentioned opacifying agent may comprise the aforementioned reflecting agent which masks the negative component and provides the requisite background for viewing the transfer image formed thereover. Where this reflecting agent does not by itself provide the requisite opacity it may be employed in combination with an additional opacifying agent in order to prevent further exposure of the light-sensitive silver halide layer or layers by actinic light incident thereon.

As examples of such integral negative-positive film units for preparing color transfer images viewable without separation as reflection prints, mention may be made of those described and claimed in US. Patents Nos. 3,415,644, 3,415,645, 3,415,646 and 3,473,925; as well as those described in copending applications Ser. Nos. 782,056 (now US. Patent No. 3,573,043) and 782,075 (now US. Patent No. 3,573,044), filed Dec. 9, 1968, 65,084, filed Aug. 19, 1970, all in the name of Edwin H. Land; and Ser. Nos. 39,646 and 39,666 of Howard G. Rogers, filed May 22, 1970, now US. Patents Nos. 3,594,165 and 3,594,164, respectively.

In general, the film units of the foregoing description, e.g., those described in the aforementioned patents and/ or copending applications, are exposed to form a developable image and thereafter developed by applying the appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is transferred, at least in part by diffusion, to the dyeable stratum to impart thereto the desired color transfer image, e.g., a positive color transfer image. Common to all of these systems is the provision of a reflecting layer between the dyeable stratum and the photosensitive strata to mask effectively the latter and to provide a background for viewing the color image contained in the dyea-ble stratum, whereby this image is viewable without separation, from the other layers or elements of the film unit. In certain of these systems, this reflecting layer is provided prior to photoexposure, e.g., as a preformed layer included in the essential layers of the laminar structure comprising the film unit, and in others it is provided at some time thereafter, e.g., by including a suitable light-reflecting agent, for example, a white pigment such as titanium dioxide, in the processing composition which is applied between the dyeable stratum and the next adjacent layer to develop the latent image and to form the color transfer image.

The dye image-providing materials which may be employed in such processes generally are selected from those materials heretofore mentioned and disclosed in the illustrative patents which were initially soluble or diifusible in the processing composition but which are selectively rendered non-diifusible as a function of development or those which are initially insoluble or non-diffusible in the processing composition but are selectively rendered diffusible as a function of development. These materials may barrier which is not as rapidly permeable upon contact be complete dyes or dye intermediates, e.g., color couplers.

In integral negative-positive film units such as those described above it is frequently desirable to incorporate a development restrainer, e.g., one of the known relatively soluble and diffusible heterocyclic mercaptan restrainers, in the positive component. As examples of such reagents mention may be made of the mercaptotetrazoles, e.g., 1-phenyl5-mercaptotetrazole and its analogs, the mercaptobenzothiazoles, e.g., 2 -mercaptobenzothiazole and its analogs, etc. The development restrainer may be incorporated in the dyeable stratum itself and/or in an associated layer, e.g., in a layer adjacent to the surface of the dyeable stratum opposed from the negative component. However incorporation of the development restrainer in the positive component of these unitary film units inherently gives rise to the aforementioned contamination problem which is not present where the positive component is maintained separately during storage, thereby precluding premature migration of the water-soluble reagent to the negative component.

In accordance with this invention, this problem of contamination is effectively inhibited, if not totally eliminated, by incorporating between the restrainer and the negative component a layer which effectively inhibits this unwanted premature migration of diffusion, but yet permits the migration when needed during the development process. This layer, which may be termed a temporary barrier for the development restrainer, is characterized as being substantially impervious to moisture but alkali permeable. The permeability to alkali may be obtained by means of an opening up or swelling induced by neutralization and/ or alkali-catalyzed hydrolysis.

Where the development restrainer is needed fairly early in the development and transfer image formation process, e.g., within several seconds, the layer should swell or open up fairly rapidly upon application of an alkaline medium, so as to permit rapid diffusion of the development restrainer through this layer. However, where the development restrainer should ideally not diffuse and hence restrain development too soon after development is initiated, it may be advantageous to employ a temporary with alkali. For example, in systems employing dye developers, it is known that the dye developers are not as diifusible in the cold, and hence development should not be restrained as rapidly in the cold as, for example, at room temperature or higher temperatures. Accordingly, it may be advantageous to employ a temporary barrier layer which is not as swellable by alkali in the cold.

In general, useful materials for forming the temporary barrier layer of the foregoing description are per se known and will be apparent to those skilled in the art in the light of this description. As examples of such materials, mention may be made of copolymers of styrene and maleic anhydride, polymeric esters which are rapidly hydrolyzed by alkali such as mono-, dior trichloroacetyl derivatives of polyvinyl alcohol, copolymers of acrylic esters and acrylic acids, e.g., copolymers of butyl methacrylate and methacrylic acid, etc.

While the thickness of the temporary barrier layer may vary according to its composition and effectiveness, the diffusibility of the development restrainer, as well as the particular photographic system and/or film units employed, in general they be applied at a coverage of about 10-200 mgm./ft.

FIG. 1 illustrates a typical integral negative-positive film unit contemplated by this invention. The film unit is shown to comprise, as the essential layers, a layer 13 of cyan dye developer, red-sensitive silver halide emulsion layer 14, iuterlayer 15, a layer of magenta dye developer 16, green-sensitive silver halide emulsion layer -17, interlayer 18, yellow dye developer layer 19, blue-sensitive silver halide emulsion layer 20, auxiliary layer 21, a temporary barrier layer 22, image-receiving layer or dyeable stratum 23 containing a development restrainer, spacer layer 24, and a pH-reducing or neutralizing layer 25. Layers '13-21 comprise the negative component and layers 23-25 comprise the positive component. These essential layers are shown to be confined between a dimensionally stable layer or support member 12 which is preferably opaque so as to permit development in the light and dimensionally stable layer or support member 26 which is effectively transparent to permit viewing of a color transfer image formed as a function of development in receiving layer or dyeable stratum 23.

FIG. 2 illustrates another film unit of this invention. As shown in this figure, the temporary barrier layer is disposed on the other side of the dyeable stratum, i.e., on the side of the dyeable stratum opposed from the negative component. It will be noted that in the film unit of FIG. 1, the development restrainer can be present in any of the layers of the positive component and is in fact shown for purposes of illustration as being in dyeable stratum 23.

However, in the film unit of FIG. 2, the development restrainer obviously cannot be in the dyeable stratum. It can, however, be disposed in barrier layer 22 or in any underlying layer, e.g., layers 24 and/or 25 or in an additional layer (not shown) disposed between layer 22 and support 26. In one preferred form of such a film unit, the restrainer is disposed in layer 24.

Layers 12 and 26 are preferably dimensionally stable liquid-impermeable layers which when taken together may possess a processing composition solvent vapor permeably sufficient to effect, subsequent to substantial transfer image formation and prior to any substantial environmental image degradation to which the resulting image may be prone, osmotic transpiration of processing composition solvent in a quantity effective to decrease the solvent from a first concentration at which the color-providing material is difi'usible to a second concentration at which it is not. Although these layers may possess a vapor transmission rate of 1 or less gms./24 hrs/100 in. /mil., they preferably possess a vapor transmission rate for the processing composition solvent averaging not less than about 100 gms./24 hrs/100 in. /mil., most preferably in terms of the preferred solvent, water, a vapor transmission rate averaging in excess of about 300 gms. of water/24 hrs/100 in. /mil., and may advantageously comprise a microporous polymeric film possessing a pore distribution which does not unduly interfere with the dimensional stability of the layers or, where required, the optical characteristics of such layers. As examples of useful materials of this nature, mention may be made of those having the aforementioned characteristics and which are derived from ethylene glycol terephthalic acid; vinyl chloride polymers; polyvinyl acetate; cellulose derivatives, etc. As heretofore noted layer 12 is of sufficient opacity to prevent fogging from occurring by light passing therethrough, and layer 26 is transparent to permit photoexposure and for viewing of a transfer image formed on receiving layer 23.

The silver halide layers preferably comprise photosensitive silver halide, e.g., silver chloride, bromide or iodide or mixed silver halides such as silver iodobromide or chloriodobromide dispersed in a suitable colloidal binder such as gelatin and such layers may typically be on the order of 0.6 to 6 microns in thickness. It will be appreciated that the silver halide layers may and in fact generally do contain other adjuncts, e.g., chemical sensitizers such as are disclosed in U.S. Pats. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; etc.; as well as other additives performing specific desired functions, e.g., coating aids, hardeners, viscosity-increasing agents, stabilizers, preservatives, ultraviolet absorbers and/or speed-increasing compounds. While the preferred binder for the silver halide is gelatin, others such as albumin, casein, zein, resins such as cellulose derivatives, polyacrylamides, vinyl polymers, etc., may replace the gelatin in whole or in part.

The respective dye developers, which may be any of those heretofore known in the art and disclosed for example in U.S. Pat. No. 2,983,606, etc, are preferably dispersed in an aqueous alkaline permeable polymeric binder, e.g., gelatin as a layer from about 1 to 7 microns in thickness.

Interlayers 15, 18 and 21 may comprise an alkaline permeable polymeric material such as gelatin and may be on the order of from about 1 to microns in thickness. As examples of other materials for forming these interlayers, mention may be made of those disclosed in U.S. Pat. No. 3,421,892 and the copending applications of Richard J. Haberlin, Ser. No. 854,491, filed Sept. 2, 1969, now U.S. Pat. No. 3,615,422, and Lloyd D. Taylor, Ser. No. 790,648, filed I an. 13, 1969, now U.S. Pat. No. 3,57 5,- 700, etc. These interlayers may also contain additional reagents performing specific functions and the various ingredients necessary for development may also be contained initially in such layers in lieu of being present 10 initially in the processing composition, in which event the desired developing composition is obtained by contacting such layers with the solvent for forming the processing composition, which solvent may include the other necessary ingredients dissolved therein.

The image-receiving layer may comprise any of the dyeable strata heretofore known in the art for preparing color transfer images. -It may be on the order of 0.25 to 0.4 mil. in thickness and may, for example, comprise a dyeable polymer such as nylon, e.g., N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with filler as, for example, onehalf cellulose acetate and one-half oleic acid; gelatin; polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, etc. The receiving layers may, if desired, contain suitable mordants, e.g., any of the conventional mordant materials for acid dyes such as those disclosed, for example, in the aforementioned U.S. Pat. No. 3,227,550; as well as other additives such as ultraviolet absorbers, pH-reducing substances, etc.

While not necessary to the practice of this invention, with the film units employing color-providing materials such as dye developers wherein development is effected in the presence of a processing composition having a relatively high pH, say, for example, on the order of at least 12 to 14, it may be desirable or expedient to provide means for reducing the pH following development to a level wherein the resulting dye image is not adversely affected. The film unit shown in the illustrative drawing shows such pH-reducing means as comprising spacer layer 24 and neutralizing layer 25. The concept of employing such pH-reducing means is disclosed, for example, in U.S. Pat. No. 3,362,819.

One such system as is disclosed in U.S. Pat. No. 3,362,- 819 employs a polymeric acid layer in association with the image-receiving layer. An inert timing or spacer layer is preferably disposed between the polymeric acid layer and the image-receiving layer.

As is disclosed in this patent, the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium, potassium, etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acid-yielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. The acid-reacting group is, of course, non-diffusible from the acid polymer layer. In the preferred embodiments disclosed, the acid polymer contains free carboxyl groups and the transfer processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, being insoluble in water in the free acid form, and by forming water-soluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anhydride groups, at least some of which preferably have been converted to free carboxyl groups prior to imbibition. While the most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used. As examples of specific polymeric acids set forth in the application, mention may be made of dibasic acid half-ester derivatives of cellulose, which derivatives contain free carboxyl groups, e.g., cellulose acetate hydrogen phthalate, cellulose acetate hydrogen glutarate, cellulose acetate hydrogen succinate, ethyl cellulose hydrogen succinate, ethyl cellulose acetate hydrogen succinate, cellulose acetate hydrogen succinate hydrogen phthalate; ether and ester derivatives or cellulose modified with sulfoanhydrides, e.g., with ortho-sulfobenzoic anhydride; polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxy or sulfo substituted aldehydes, e.g., m-, or p-benzaldehyde sulfonic acid or carboxylic acid; partial esters of ethylene/ maleic anhydride copolymers; partial esters of methylvinyl ether/maleic anhydride copolymers; etc.

As previously noted, the pH of the processing composition may be of the order of at least 12 to 14. The acid polymer layer is disclosed to contain at least sufficient acid groups to effect a reduction in the pH of the image layer from a pH of about 12 to 14 to a pH of at least 11 or lower at the end of the inbibition period, and preferably to a pH of about to 8 within a short time after imbibition, thus requiring, of course, that the action of the polymeric acid be accurately so controlled as not to interfere with either development of the negative of image transfer of the color-providing material. For this reason, the pH of the image layer must be kept at a functional transfer level until dye image has been formed. Where the color-providing material is not diffusible at the lower pH obtained by the polymeric acid layer, the subsequent pH reduction, in addition to its desirable effect upon image light stability, also serves a highly valuable photographic function by substantially terminating further dye transfer.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, by an undesired reduction in positive image density, the acid groups are disclosed to be so distributed in the acid polymer layer that the rate of their availability to the alkali is controllable, e.g., as a function of the rate of swelling of the polymer layer, which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired distribution of the acid groups in the acid polymer layer may be effected by mixing the acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, or by using only the acid polymer but selecting one having a relatively lower proportion of acid groups. These embodiments are illustrated, respectively, in the cited copending patent, by (a) a mixture of cellulose acetate and cellulose acetate hydrogen phthalate and (b) a cellulose acetate hydrogen phthalate polymer having a much lower percentage of phthalyl groups than the first-mentioned cellulose acetate hydrogen phthalate.

It is also there disclosed that the layer containing the polymeric acid may contain a water-insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats are employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer, for example, a layer comprising polyvinyl alcohol or gelatin, acts to time control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. It is there stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer, but the pH drops quite rapid- 1y once the alkali diffuses through the spacer layer.

As disclosed in aforementioned U.S. Patent No. 3,362,- 819, the presence of an inert spacer layer was found to be effective in evening out the various reaction rates over a wide range of temperatures, for example, by preventing premature pH reduction when imbibition is effected at temperatures above room temperature, for example, at 95 to 100 F. By providing an inert spacer layer, that application discloses that the rate at which alkali is available for capture in the polymeric acid layer becomes a function of the alkali diffusion rate.

However, as disclosed in US. Patent No. 3,455,686 preferably the aforementioned rate at which the cations of the alkaline processing composition, i.e., alkali ions, are available for capture in the polymeric acid layer should be decreased with increasing transfer processing temperatures in order to provide diffusion transfer color processes relatively independent of positive transfer image variations over an extended range of ambient temperatures.

Specifically, it is there stated to have been found that the diffusion rate of alkali through a permeable inert polymeric spacer layer increases with increased processing temperature to the extent, for example, that at relatively high transfer processing temperatures, that is, transfer processing temperatures above approximately F., a premature decrease in the pH of the transfer processing composition occurs due, at least in part, to the rapid diffusion to alkali from the dye transfer environment and its subsequent neutralization upon contact with the polymeric acid layer. This was stated to be especially true of alkali traversing an inert spacer layer possessing permeability to alkali optimized to be effective with the temperature range of optimum transfer processing. Conversely, at temperatures below the optimum transfer processing range, for example, temperatures below approximately 40 F., the last-mentioned inert spacer layer was disclosed to provide an effective diffusion barrier timewise preventing effective traverse of the inert spacer layer by alkali having temperature depressed diffusion rates and to result in maintenance of the transfer processing environments high pH for such extended time interval as to facilitate formation of transfer image stain and its resultant degradation of the positive transfer images color definition.

It is further stated in the last-mentioned US. Pat. No. 3,455,686 to have been found, however, that if the inert spacer layer of the print-receiving element is replaced by a spacer layer which comprises a permeable polymeric layer exhibiting permeability inversely dependent on temperature, that is, a polymeric film-forming material which exhibits decreasing permeability to solubilized alkali derived cations such as alkali metal and quaternary ammonium ions under conditions of increasing temperature, that the positive transfer image defects resultant from the aforementioned overextended pH maintenance and/ or premature pH reduction are obviated.

As examples of polymers which were disclosed to exhibit inverse temperature-dependent permeability to alkali, mention may be made of: hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyvinyl oxazolidone, hydroxypropyl methyl cellulose, isopropyl cellulose, partial acetals of polyvinyl alcohol such as partial polyvinyl butyral, partial polyvinyl formal, partial polyvinyl acetal, partial polyvinyl propional, and the like.

The last-mentioned specified acetals of polyvinyl were stated to generally comprise saturated aliphatic hydrocarbon chains of a molecular weight of at least 1,000, preferably of about 1,000 to 50,000, possessing a degree of acetalation within about 10% to 30%, 10% to 30%, 20% to 80% and 10% to 40%, of the polyvinyl alcohols theoretical polymeric hydroxy groups, respectively, and including mixed acetals where desired.

Where desired, a mixture of the polymers is to be employed, for example, a mixture of hydroxypropyl methyl cellulose and partial polyvinyl butyral.

While the acid-containing or neutralizing layer 25 and spacer or timing layer 24 of the foregoing description are shown in the illustrative figures to be disposed between the receiving layer and transparent layer 26, this pH- reducing .means may be disposed elsewhere in the film unit and may, for example, be disposed between the receiving layer and layer 12, as is disclosed in the copending application of Edwin H. Land, Ser. No. 782,056, filed Dec. 9, 1968, now US. Pat. No. 3,573,043.

The structural integrity of the film unit may be maintained by an adhesive capability installed between the various layers comprising the laminate. However, the adhesive capability installed between barrier layer 22 and auxiliary layer 21 should be less than that between the opposed surfaces of the remainder of the layers forming the laminate so as to permit the processing fluid to be applied therebetween. The laminates structural integrity may also be enhanced or provided by a binding member extending around the edges of the laminate, and maintaining the layers comprising the laminate intact, except at the interface between layers 22 and 21 during distribution of the processing fluid between those layers.

The processing fluid may be contained in a pod or rupturable container of the type shown and described in any of U.S. Pats. Nos. 2,543,181; 2,634,886; 2,653,732; 2,723,051; 3,056,492; 3,056,491; 3,152,515; and the like. In general, such containers will comprise a rectangular blank of fluidand air-impervious sheet material folded longitudinally upon itself to form two walls which are sealed so as to form a cavity for containing the processing composition.

The processing composition may comprise an aqueous alkaline solution having a pH at which the dye developers are soluble and diffusible and an opacifying agent in a quantity suflicient to mask the dye developers associated with the silver halide emulsions after processing and to provide the requisite background for viewing the color image formed in layer 23. As mentioned before, the concentration of opacifying agent is preferably sufficient to protect the film products silver halide emulsion or emulsions from further exposure by actinic radiation traversing through the dimensionally stable transparent layer 26 after the opacifying agent is applied to the emulsion(s). Accordingly, where layer 12 is opaque, the film product may be processed, after distribution of the composition, in the presence of actinic radiation, in view of the fact that the silver halide emulsion or emulsions of the laminate are appropriately protected at one major surface by the opaque processing composition and at the remaining major surface by the dimensionally stable opaque layer. Any edge leakage of actinic radiation incident on the emulsion or emulsions may also be prevented by the use of appropriate means such as opaque binder tapes.

A preferred opacification system to be contained in the processing composition is that described in the copending application of Edwin H. Land, Ser. No. 43,782, filed June 5, 1970, and now abandoned, comprising an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective, when the process- 1ng composition is applied, to provide a layer exhibiting optical transmission density than about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density than about 1.0 density with respect to incident visible radiation.

In lieu of having the reflecting pigment contained in the processing composition, e.g., as disclosed in the aforementroned copending application Ser. No. 43,782, and now abandoned, the reflecting pigment needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in receiving layer 23 may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed on the copending applications of Edwin H. Land, Ser. Nos. 846,441, filed July 31, 1969, now U.S. Pat. No. 3,615,421, and 3,645, filed Jan. 19, 1970, now U.S. Pat. No. 3,620,724. The reflecting pigment may be generated in srtu as is disclosed in the copending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742, both filed June 5, 1970, now U.S. 'Pats. Nos. 3,647,434 and 3,647,- 435, respectively.

The following example illustrates the preparation of a typical polymeric material which may be employed as the temporary barrier layer.

14 Example 1 142 g. of butyl methacrylate and 86 g. of methacrylic acid were dissolved in 700 cc. of tetrahydrofuran. 2.28 g. of azobis-iso-butyronitrile were then added as catalyst. The resulting solution was heated under reflux for 20 hours to yield the copolymer of butyl methacrylate and methacrylic acid. The polymer may be recovered from the reaction mixture or the mixture may be used directly, preferably by dilution with solvent, in the preparation of the film unit.

A film unit similar to that shown in FIG. 1 may be prepared, for example, by coating, in succession, on a gelatin subbed, 4 mil. opaque polyethylene terephthalate film base, the following layers:

(1) A layer of cyan dye developer dispersed in gelatin and coated at a coverage of about mgs./ft. of dye and about mgs./ft. of gelatin;

(2) A red-sensitive gelatino-silver iodobromide emulsion coated at a coverage of about 225 mgs./ft. of silver and about 50 m-gs./ft. of gelatin;

3) A layer of acrylic latex sold by Rohm and Haas Co. under the trade designation A061 and polyacrylamide coated with a coverage of about 100 mgs./ft. of AC-6l and about 5 mgs./l:'t. of polyacrylamide;

(4) A layer of magenta dye developer dispersed in gelatin and coated at a coverage of 70 mgs./ft. of dye and about mgs./ft. of gelatin;

(5) A green-sensitive gelatino-silver iodobromide emulsion coated in a coverage of about 120 mgs./ft. of silver and 60 mgs./ft. of gelatin;

6) A layer comprising the acrylic latex sold by Rohm and Haas C0. under the trade designation B-15 and polyacrylamide coated in a coverage of about 100 mgs./ft. of B-l5 and about 10 mgs./ft. of polyacrylamide;

(7) A layer of a yellow dye developer and the auxiliary developer 4' methylphenyl hydroquinone dispersed in gelatin and coated at a coverage of about 50 mgs./ft. of dye, about 15 mgsJft. of auxiliary developer and 50 rugs/ft. of gelatin;

(8) A blue-sensitive gelatino-silver iodobromide emulsion coated at a coverage of about 75 mgs./ft. of gelatin; and

(9) A layer of gelatin coated at a coverage of about 50 mgsJft. of gelatin.

The three dye developers employed above may be the following:

a cyan dye developer;

HO-CH:CE: Q

/NS02 N=N -l CH3 HO-CHz-CH: I l N O O I 0 z K2120 0 0 OH I l OCGHz-CH2 a magenta dye developer; and

?C3H7 N02 l\-Hzo I) T OH ml-CiEb-Cfih a yellow dye developer.

Then a transparent 4 mil. polyethylene terephthalate film base may be coated, in succession, with the following illustrative layers:

(1) a 7:3 mixture, by weight, of polyethylene/maleic acid copolymer and polyvinyl alcohol at a coverage of about 1400 mgs./ft. to provide a polymeric acid neutralizin-g layer;

(2) a graft copolymer of acrylamide and diacetone acrylamide on a polyvinyl alcohol backbone in a molar ratio of 1:3.2:1 at a coverage of about 800 mgs./ft. to provide a polymeric spacer or timing layer;

(3) a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 900 mgs./ft. and including about 20 mgs./ft. of l-phenyl-S-mercaptotetrazole, to provide a polymeric image-receiving layer containing development restrainer; and

(4) an overlayer of the polymer prepared in the illustrative example at a coverage of about 100 mgs./ift.

The two components may then be laminated together to provide an integral film unit of the type shown in FIG. 1.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution comprising the following proportions of ingredients:

Benzotriazole, gms

OH H H W 11-C12H25 O I (B), Ems 0. 52

&

(C), gms. 11.8

may then be fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes interconnecting the respective containers and laminates, such that, upon application of compressive pressure to a container, its contents may be distributed, upon rupture of the containers marginal seal, between the temporary barrier layer and the next adjacent layer of the negative component.

An integral negative-positive film unit containing the temporary barrier of this invention, e.g., a film unit as illustrated above and shown in FIG. 1, was found to inhibit substantially the aforementioned contamination problem caused by the undesired premature diffusion of the development restrainer to the negative component.

Since the problem of contamination is most evident and most serious after storage under heat and humidity, heathumidity tests were run comparing the film unit of this invention with a control unit similar in all respects except it had no temporary barrier layer and also with a print obtained by exposing a photosensitive element having the same negative component (but no positive component) and then developing in superposition with a separate image-receiving element containing the positive component, the respective elements in the latter control test being maintained separately until development so that no contamination could occur. The respective film units were first stored for five days at 100 F., relative humidity, and then exposed and developed under the same 17 control conditions for proper evaluation of the results. The respective D and Dmax, readings were then obtained in standard manner for the cyan, magenta and yellow dyes in the prints obtained from these tests.

The results are as follows:

Dmin- Dm:

Film unit with temporary barrier:

O 19 l. 86 26 2. 03 Y 42 2. 06 Control-no temporary ba With reference first to the respective D it will be seen that the film unit of this invention afforded significant improvement over the yellow D obtained with the same film unit containing no temporary barrier, specifically, the D (unwanted yellow dye transfer) obtained from the film unit of this invention was less than half that obtained with the control. On the other hand, it was only slightly higher than that obtained from the other control wherein the positive and negative components were contained separately to preclude contamination, indicating that only a very slight contamination occurred. The other Dmms. of all three prints were substantially the same, indicating that in these particular tests, the only noticeable contamination occurred in the blue-sensitive silver halide layer, the closest silver halide layer to the positive component. [Note: In other tests, employing the control film unit with no temporary barrier, contamination to a lesser extent has also been observed in the other two silver halide layers] With reference to the Dmax, readings, the film unit of this invention provided a slightly greater D for all three dyes than did the control with no temporary barrier, indicating clearly that the barrier did not inhibit or in any way adversely affect the image dye transfer from the negative component to the underlying dyeable stratum.

A film unit of the type shown in FIG. 2 may be prepared by the procedure described previously for the preparation of a film unit of FIG. 1, modifying the positive component by coating over the polymeric acid neutralizing layer, a layer containing a graft copolymer of acrylamide and diacetone acrylamide on a polyvinyl alcohol backbone in a molar ratio of 1:3.2:l at a coverage of about 900 mgs./ft. and about 45 mgs./ft. of 1- phenyl-S-mercaptotetrazole to provide a spacer or timing layer including the development restrainer; applying over this layer a temporary barrier layer comprising about 60 mgs./ft. of Lytron 810 (trademark of Monsanto Company for a styrene/maleic anhydride copolymer); and then applying the dyeable stratum. The resulting positive component may then be laminated to the negative component to provide an integral film unit of the type shown in FIG. 2.

Tests conducted after storage for five days at 100 F., 80% relative humidity showed that this film unit, like the one of FIG. 1, obviated the aforementioned problem of contamination; Whereas a film unit similar in all respects except that it did not contain the temporary barrier layer evidenced severe contamination of the blue-sensitive emulsion.

As was mentioned previously, it is also possible to employ the development restrainer in the temporary barrier layer, rather than in an underlying layer. A film unit of this type may be provided by applying on the polyethylene terephthalate film base the neutralizing and timing layers noted previously; then applying a layer containing about be laminated to the negative component to provide the desired integral negative-positive film unit. A film unit of this description also evidenced no contamination after storage for five days at 100 F., relative humdity.

While reference has been made in the foregoing description, including the illustrative drawing, to those integral negative-positive film units wherein the negative and positive components are maintained together, e.g., by lamination and/ or physical means such as a binding tape, during storage, exposure, processing and thereafter as a composite print, it will be appreciated that the invention is not so restricted, but is equally adaptable to those systems wherein the positive and negative components are maintained in superposition during storage so as inherently to cause the contamination problem to which this invention is directed, but are not necessarily maintained together thereafter. For example, the invention is also applicable to systems wherein the negative and positive components are maintained together during storage, separated during photoexposure, and thereafter brought back in superposition for processing. The respective components may then be maintained together following processing to provide a composite print or they may be separated to provide the desired transfer image. The invention is also adaptable, for example, to systems wherein the positive and negative components are initially laminated together, as has been described, but are separated following transfer image formation.

From the foregoing description it will be seen that the present invention provides an efficient means for diminishing materially, if not precluding the problems resulting from premature migration of the development restrainer to one or more light-sensitive layers in the film unit. The objectives may be accomplished without adversely affecting the dye transfer from the negative component to the dyeable stratum.

Since certain changes may be made in the above prodnet and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic product for forming color transfer images including a negative component comprising at least one light-sensitive silver halide layer and an associated dye image-providing material and a superposed positive component containing a dyeable stratum, said positive component further including a soluble and diffusible development restrainer in said dyeable stratum or in an associated layer;

the improvement which comprises disposing in said product between said development restrainer and said silver halide layer, a layer which is a temporary barrier against diffusion of said development restrainer from said positive component to said negative component, said layer being so constituted as to inhibit substantially diffusion of said development restrainer to said silver halide layer prior to application of an aqueous alkaline developing composition, but will permit such diffusion upon application of said composition.

2. A product as defined in claim 1 where said tempo-rary barrier layer comprises a polymeric material which is substantially impervious to moisture but which is alkali permeable.

3. A product as defined in claim 2 wherein said polymeric material swells by hydrolysis upon contact With alkali to permit said diffusion therethrough of said development restrainer.

4. A product as defined in claim 2 wherein said barrier action of said polymeric material inhibiting diffusion therethrough of said development restrainer is removed by neutralization in the presence of said aqueous alkaline composition.

5. A product as defined 1n claim 1 including means for applying an aqueous alkaline processing composition between said negative and positive components.

6. A product as defined in claim 5 including means for applying a layer of a light-reflecting agent between said positive and negative components, said layer of light-reflecting agent being adapted for effectively masking said negative component and for providing a background for viewing a color transfer image formed in said dyeable stratum, without separation, as a reflection print.

7. A product as defined in claim 6 wherein said lightreflecting means comprises a preformed layer disposed between said dyeable stratum and said negative component.

8. A product as defined in claim 6 wherein said lightrefiecting means is applied in a layer between said negative component and said dyeable stratum at some time following photoexposure of said film unit.

9. A product as defined in claim 2 wherein said dye image-providing material is a dye or dye intermediate which is insoluble and non-difiusible in an aqueous alkaline medium.

10. A product as defined in claim 2 wherein said dye image-providing material is soluble and difiusible in an aqueous alkaline medium.

11. A product as defined in claim 1 wherein said temporary barrier layer comprises a polymeric material selected from the group consisting of copolymers of styrene and maleic anhydride, chloroacetyl derivatives of polyvinyl alcohol and copolymers of acrylic esters and acrylic acids.

12. A product as defined in claim 11 wherein said polymer comprises a copolymer of butyl methacrylate and methacrylic acid.

13. A product as defined in claim 1 wherein said temporary barrier layer is disposed betweensaid dyeable stratum and said negative component.

14. A product as defined in claim 13 wherein said development restrainer is disposed in said dyeable stratum.

15. A product as defined in claim 1 wherein said temporary barrier layer is disposed in said product on the side of said dyeable stratum opposed from said negative component.

16. A product as defined in claim 15 wherein said development restrainer is disposed in said product in a layer adjacent the surface of said barrier layer opposed from said dyeable stratum.

17. A product as defined in claim 15 wherein said development restrainer is disposed in said barrier layer.

18. In an integral negative-positive film unit for forming color transfer images including a negative component comprising a red-sensitive silver halide layer and an associated cyan image-providing material, a green-sensitive silver halide layer and an associated magenta image-providing material, and a blue-sensitive silver halide layer and an associated yellow image-providing material; and a positive component containing a dyeable stratum for forming a color transfer image from said materials diffusing thereto from said negative component, said positive component further containing a soluble and diffusible development restrainer;

the improvement which comprises disposing in said film unit between said development restrainer and said blue-sensitive silver halide layer, a layer which is a temporary barrier against diffusion of said development restrainer from said positive component to said negative component, said layer being so constituted as to inhibit substantially diffusion of said development restrainer to said silver halide layer prior to application of an aqueous alkaline developing composition, but will permit such diffusion upon application of said composition.

19. A film unit as defined in claim 18 including a substantially transparent dimensionally stable layer disposed on the outer surface of said positive component.

20. A film unit as defined in claim 19 including means for applying a light-reflecting layer between said dyeable stratum and said negative component.

21. A film unit as defined in claim 20 wherein said means comprises a preformed layer of a light-reflecting agent.

22. A film unit as defined in claim 20 wherein said means comprises an aqueous alkaline processing composition including said light-refiecting agent.

23. A film unit as defined in claim 22 wherein said processing composition is confined in a rupturable container positioned with respect to said film unit as to be capable, upon rupturing, of discharging said composition in a substantially uniform layer between said dyeable stratum and said negative component.

24. A film unit as defined in claim 20 wherein an opaque dimensionally stable layer is disposed on the outer surface of said negative component.

25. A film unit as defined in claim 18 wherein said development restrainer is disposed in said dyeable stratum.

26. A film unit as defined in claim 18 wherein said development restrainer is a heterocyclic mercaptan.

27. A film unit as defined in claim 25 wherein said development restrainer is a mercaptotetrazole or a mercapto benzothiazole.

28. In a film unit for forming a color transfer image viewable without separation as a positive reflection print comprising, in order, an opaque dimensionally stable layer, a layer of a cyan dye developer, at red-sensitive silver halide emulsion layer, a layer of a magenta dye developer, a green-sensitive silver halide emulsion layer, a layer of a yellow dye developer, a blue-sensitive silver halide emulsion layer, a dyeable stratum, a spacer layer, a neutralizing layer and a dimensionally stable transparent layer, said film unit further including a soluble and diffusible development restrainer in said dyeable stratum or in a layer between said stratum and said transparent layer;

the improvement 'which comprises including in said film unit between said dyeable stratum and said bluesensitive silver halide emulsion layer, a layer which is a temporary barrier against diffusion of said development restrainer from said positive component to said negative component, said temporary barrier layer being so constituted as to inhibit substantially diffusion of said development restrainer to said silver halide layer prior to application of an aqueous alkaline developing composition, but will permit such diffusion upon application of said composition, said temporary barrier layer comprising a polymeric material which is substantially impervious to moisture but which is alkali permeable.

29. A film unit as defined in claim 28 wherein said development restrainer is a heterocyclic mercaptan and said polymeric material is selected from the group consisting of copolymers of styrene and maleic anhydride, chloroacetyl derivatives of polyvinyl alcohol and copolymers of acrylic esters and acrylic acids.

30. A film unit as defined in claim 29 wherein said development restrainer is of the mercaptotetrazole or mercaptobenzothiazole series.

31. A film unit as defined in claim 28 wherein said development restrainer is disposed in said dyeable stratum and said restrainer is 1-phenyl-S-mercaptotetrazole.

32. A photographic process for forming transfer images in color comprising the steps of exposing a film unit having a negative component comprising at least one lightsensitive silver halide layer and an associated dye imageproviding material and a positive component containing a dyeable stratum and a development restrainer disposed in said dyeable stratum or in an associated layer, whereby to form a developable image; providing between said negative and positive components temporary barrier means for preventing migration of said development restrainer to said negative component; applying to the thus exposed element an aqueous alkaline processing composition to initiate development of said negative component and formation of an imagewise distribution of soluble and diffusible dye image-providing material as a function of said development; at some time after said application of said aqueous alkaline processing composition and after said development and imagewise formation of dye image-providing material is substantially complete, destroying said temporary barrier means whereby to permit said development restrainer in said positive component to migrate to said negative component; diffusing said development restrainer to said negative component to inhibit effectively further development of said negative component; and transferring said imagewise distribution of dye imageproviding material, at least in part, by diffusion, to said dyeable stratum to impart thereto a color transfer image.

33. A process as defined in claim 32 wherein said dye image-providing material is soluble and diifusible in an aqueous alkaline medium but is rendered insoluble selectively as a function of development.

34. A process as defined in claim 33 wherein said dye image-providing material is a dye or dye intermediate which is insoluble and non-diffusible in an aqueous alkaline medium but which is rendered soluble and diffusible in an imagewise pattern as a function of development.

35. A process as defined in claim 32 wherein said temporary barrier means comprises a layer of a polymeric material which is substantially impervious to moisture but which is permeable to said aqueous alkaline processing 22 composition, said layer being disposed in said film unit between said dyeable stratum and said negative component.

36. A process as defined in claim wherein said development restrainer is disposed in said dyeable stratum.

37. A process as defined in claim 32 wherein said temporary barrier means comprises a layer of a polymeric material which is substantially impervious to moisture but which is permeable to said aqueous alkaline processing composition, said layer being disposed in said film unit on the side of said dyeable stratum opposed from said negative component.

38. A process as defined in claim 37 wherein said development restrainer is disposed in said film unit in a layer adjacent the surface of said barrier layer opposed from said dyeable stratum.

39. A process as defined in claim 37 wherein said development restrainer is disposed in said barrier layer.

References Cited UNITED STATES PATENTS 3,227,554 1/1966 Barr et al. 9655 ALFONSO f. SURO PICO, Primary Examiner US. Cl. X.R. 96-3, 66.3, 77 

